Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

One object of the present invention is to perform compartmental analysis
of the dynamics of a tracer in the brain, and the present invention
provides a compartmental analysis system including a measurement
apparatus that measures the strength of an electromagnetic wave from a
tracer and a compartmental analyzer that performs compartmental analysis
of the dynamics of the tracer in the brain on the basis of the strength
of the electromagnetic wave, wherein the compartmental analyzer includes
a rate constant calculation unit that calculates a rate constant when the
tracer moves between compartments on the basis of the strength of an
electromagnetic wave in a first compartment corresponding to the cerebral
blood vessel in the brain or an input function in the first compartment,
the strength of an electromagnetic wave in a second compartment
corresponding to the brain tissue in the brain, and the strength of an
electromagnetic wave in a third compartment corresponding to the cerebral
sulcus or cerebral ventricle in the brain.

Claims:

1. A compartmental analysis system that performs compartmental analysis
of dynamics of a tracer in a brain, including: a measurement apparatus
that measures a strength of an electromagnetic wave from the tracer in
the brain; and a compartmental analyzer that performs compartmental
analysis of dynamics of the tracer in the brain on the basis of the
strength of the electromagnetic wave from the tracer in the brain
measured by the measurement apparatus, wherein the compartmental analyzer
includes a rate constant calculation unit that calculates a rate constant
when the tracer moves between the compartments on the basis of a strength
of an electromagnetic wave in a first compartment corresponding to a
cerebral blood vessel in the brain measured by the measurement apparatus
or an input function in the first compartment, a strength of an
electromagnetic wave in a second compartment corresponding to brain
tissue in the brain measured by the measurement apparatus, and a strength
of an electromagnetic wave in a third compartment corresponding to a
cerebral sulcus or a cerebral ventricle in the brain measured by the
measurement apparatus.

2. The compartmental analysis system according to claim 1, wherein the
compartmental analyzer further includes a compartment-specifying unit
that specifies to which one of the compartments a part of the brain in
each of a plurality of divided regions obtained by dividing the brain
corresponds, and the rate constant calculation unit calculates the rate
constant when the tracer moves between the compartments on the basis of a
strength of an electromagnetic wave in a divided region specified to
correspond to the first compartment by the compartment-specifying unit, a
strength of an electromagnetic wave in a divided region specified to
correspond to the second compartment by the compartment-specifying unit,
and a strength of an electromagnetic wave in a divided region specified
to correspond to the third compartment by the compartment-specifying
unit.

3. The compartmental analysis system according to claim 2, wherein the
compartmental analyzer further includes a region division unit that
divides the brain into a plurality of divided regions, and the
compartment-specifying unit specifies to which one of the compartments a
part of the brain in each of the plurality of divided regions divided by
the region division unit corresponds.

4. The compartmental analysis system according to claim 3, wherein the
compartmental analyzer further includes an instruction-receiving unit
that receives an instruction to specify a region-of-interest of the
brain, which is to be subjected to compartmental analysis, and the region
division unit divides the region-of-interest, which is specified by the
instruction received by the instruction-receiving unit, into a plurality
of divided regions.

5. The compartmental analysis system according to claim 1, wherein the
tracer is H.sub.2.sup.17O.

6. The compartmental analysis system according to claim 1, wherein the
measurement apparatus is an MRI apparatus.

7. A compartmental analysis method of performing compartmental analysis
of dynamics of a tracer in a brain on the basis of a strength of an
electromagnetic wave from the tracer in the brain measured by a
measurement apparatus, wherein the method includes: a step of calculating
a rate constant when the tracer moves between the compartments on the
basis of a strength of an electromagnetic wave in a first compartment
corresponding to a cerebral blood vessel in the brain measured by the
measurement apparatus or an input function in the first compartment, a
strength of an electromagnetic wave in a second compartment corresponding
to brain tissue in the brain measured by the measurement apparatus, and a
strength of an electromagnetic wave in a third compartment corresponding
to a cerebral sulcus or a cerebral ventricle in the brain measured by the
measurement apparatus.

8. A compartmental analyzer that performs compartmental analysis of
dynamics of a tracer in a brain on the basis of a strength of an
electromagnetic wave from the tracer in the brain measured by a
measurement apparatus, wherein the compartmental analyzer includes: a
rate constant calculation unit that calculates a rate constant when the
tracer moves between the compartments on the basis of a strength of an
electromagnetic wave in a first compartment corresponding to a cerebral
blood vessel in the brain measured by the measurement apparatus or an
input function in the first compartment, a strength of an electromagnetic
wave in a second compartment corresponding to brain tissue in the brain
measured by the measurement apparatus, and a strength of an
electromagnetic wave in a third compartment corresponding to a cerebral
sulcus or a cerebral ventricle in the brain measured by the measurement
apparatus.

9. A program causing a computer to function as a compartmental analyzer
that performs compartmental analysis of dynamics of a tracer in a brain
on the basis of a strength of an electromagnetic wave from the tracer in
the brain measured by a measurement apparatus, wherein the program causes
the computer to function as: a rate constant calculation unit that
calculates a rate constant when the tracer moves between the compartments
on the basis of a strength of an electromagnetic wave in a first
compartment corresponding to a cerebral blood vessel in the brain
measured by the measurement apparatus or an input function in the first
compartment, a strength of an electromagnetic wave in a second
compartment corresponding to brain tissue in the brain measured by the
measurement apparatus, and a strength of an electromagnetic wave in a
third compartment corresponding to a cerebral sulcus or a cerebral
ventricle in the brain measured by the measurement apparatus.

10. A recording medium recording a program causing a computer to function
as a compartmental analyzer that performs compartmental analysis of
dynamics of a tracer in a brain on the basis of a strength of an
electromagnetic wave from the tracer in the brain measured by a
measurement apparatus, wherein the recording medium records a program
causing the computer to function as: a rate constant calculation unit
that calculates a rate constant when the tracer moves between the
compartments on the basis of a strength of an electromagnetic wave in a
first compartment corresponding to a cerebral blood vessel in the brain
measured by the measurement apparatus or an input function in the first
compartment, a strength of an electromagnetic wave in a second
compartment corresponding to brain tissue in the brain measured by the
measurement apparatus, and a strength of an electromagnetic wave in a
third compartment corresponding to a cerebral sulcus or a cerebral
ventricle in the brain measured by the measurement apparatus.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a compartmental analysis system, a
compartmental analysis method, a compartmental analyzer, a program, and a
recording medium. In particular, the present invention relates to a
compartmental analysis system that performs compartmental analysis of the
dynamics of a tracer in the brain, a compartmental analysis method and a
compartmental analyzer that perform compartmental analysis of the
dynamics of a tracer in the brain on the basis of the strength of an
electromagnetic wave from a tracer in the brain measured by a measurement
apparatus, a program causing a computer to function as the compartmental
analyzer, and a recording medium on which the program is recorded.

[0003] 2. Description of Related Art

[0004] Diseases, such as cerebrovascular disorder or dementia, may be
evaluated using cerebral blood flow as an index. As a method of analyzing
the cerebral blood flow, a method of performing compartmental analysis of
the dynamics of cerebral blood flow exuded from cerebral blood vessels is
known (for example, refer to Michio Senda, "The 20th influx and
distribution volume", [online], December 2009, nuclear medicine document
information seminar, [accessed on Oct. 6, 2011], the Internet,
<URL:http://www.asca-co.com/nuclear/2009/12/post-22.html> and
Michio Senda, "The 24th imaging of cerebral blood flow and metabolism",
[online], April 2010, nuclear medicine document information seminar,
[accessed on Oct. 6, 2011], the Internet,
<URL:http://www.asca-co.com/nuclear/2010/04/post-26.html>). More
specifically, the dynamics of cerebral blood flow is measured by positron
emission tomography using a radioactive chemical as a tracer, for
example. In addition, the dynamics of cerebral blood flow is analyzed by
a two-compartment model formed by two compartments of cerebral blood
vessels and brain tissue. In the analysis using the two-compartment
model, it is assumed that all arterial blood arriving at a section of the
brain moves to the brain tissue.

[0005] In the method of analyzing the dynamics of cerebral blood flow
using the two-compartment model, a detailed anatomical stereoscopic image
of the patient's brain, that is, a morphological image, is generally
captured by an X-ray CT (Computed Tomography) apparatus. In addition,
each region of the cerebral blood vessels and brain tissue in which the
dynamics of cerebral blood flow needs to be analyzed is determined with
reference to the image captured by the X-ray CT apparatus. Then, a
functional image of the brain is captured by injecting a radioactive
chemical as a tracer into the patient. Then, a temporal change in the
amount of radiation in each region of the cerebral blood vessels and
brain tissue is measured. In addition, a rate constant K1 when the tracer
moves from the cerebral blood vessel to the brain tissue and a rate
constant K2 when the tracer moves from the brain tissue to the cerebral
blood vessel are calculated on the basis of the measured amount of
radiation. In addition, the calculated rate constants K1 and K2 are used
to calculate the cerebral blood flow (which means the amount of
radioactive tracer that flows from the blood vessel and reaches the brain
cell tissue).

[0006] The rate constants K1 and K2 calculated by the analysis using the
two-compartment model are useful parameters to analyze the dynamics of
cerebral blood flow in the brain. Here, the dynamics of cerebral blood
flow in the brain is associated with the dynamics of cerebrospinal fluid
in the cerebral sulcus or cerebral ventricle. However, the analysis using
the two-compartment model described above focuses on only the dynamics of
a tracer between cerebral blood vessels and brain tissue. Therefore, it
is difficult for very useful parameters to analyze the dynamics of
cerebral blood flow in the brain to be calculated.

SUMMARY OF THE INVENTION

[0007] In order to solve the above-described problems, according to a
first aspect of the invention, a compartmental analysis system that
performs compartmental analysis of dynamics of a tracer in a brain
includes: a measurement apparatus that measures a strength of an
electromagnetic wave from the tracer in the brain; and a compartmental
analyzer that performs compartmental analysis of dynamics of the tracer
in the brain on the basis of the strength of the electromagnetic wave
from the tracer in the brain measured by the measurement apparatus,
wherein the compartmental analyzer includes a rate constant calculation
unit that calculates a rate constant when the tracer moves between the
compartments on the basis of a strength of an electromagnetic wave in a
first compartment corresponding to a cerebral blood vessel in the brain
measured by the measurement apparatus or an input function in the first
compartment, a strength of an electromagnetic wave in a second
compartment corresponding to brain tissue in the brain measured by the
measurement apparatus, and a strength of an electromagnetic wave in a
third compartment corresponding to a cerebral sulcus or a cerebral
ventricle in the brain measured by the measurement apparatus.

[0008] The compartmental analyzer may further include a
compartment-specifying unit that specifies to which one of the
compartments a part of the brain in each of a plurality of divided
regions obtained by dividing the brain corresponds. The rate constant
calculation unit may calculate the rate constant when the tracer moves
between the compartments on the basis of a strength of an electromagnetic
wave in a divided region specified to correspond to the first compartment
by the compartment-specifying unit, a strength of an electromagnetic wave
in a divided region specified to correspond to the second compartment by
the compartment-specifying unit, and a strength of an electromagnetic
wave in a divided region specified to correspond to the third compartment
by the compartment-specifying unit.

[0009] The compartmental analyzer may further include a region division
unit that divides the brain into a plurality of divided regions, and the
compartment-specifying unit may specify to which one of the compartments
a part of the brain in each of the plurality of divided regions divided
by the region division unit corresponds.

[0010] The compartmental analyzer may further include an
instruction-receiving unit that receives an instruction to specify a
region-of-interest of the brain, which is to be subjected to
compartmental analysis, and the region division unit may divide the
region-of-interest, which is specified by the instruction received by the
instruction-receiving unit, into a plurality of divided regions.

[0011] The tracer may be H217O.

[0012] The measurement apparatus may be an MRI apparatus.

[0013] According to a second aspect of the invention, a compartmental
analysis method of performing compartmental analysis of dynamics of a
tracer in a brain on the basis of a strength of an electromagnetic wave
from the tracer in the brain measured by a measurement apparatus
includes: a step of calculating a rate constant when the tracer moves
between the compartments on the basis of a strength of an electromagnetic
wave in a first compartment corresponding to a cerebral blood vessel in
the brain measured by the measurement apparatus or an input function in
the first compartment, a strength of an electromagnetic wave in a second
compartment corresponding to brain tissue in the brain measured by the
measurement apparatus, and a strength of an electromagnetic wave in a
third compartment corresponding to a cerebral sulcus or a cerebral
ventricle in the brain measured by the measurement apparatus.

[0014] According to a third aspect of the invention, a compartmental
analyzer that performs compartmental analysis of dynamics of a tracer in
a brain on the basis of a strength of an electromagnetic wave from the
tracer in the brain measured by a measurement apparatus includes: a rate
constant calculation unit that calculates a rate constant when the tracer
moves between the compartments on the basis of a strength of an
electromagnetic wave in a first compartment corresponding to a cerebral
blood vessel in the brain measured by the measurement apparatus or an
input function in the first compartment, a strength of an electromagnetic
wave in a second compartment corresponding to brain tissue in the brain
measured by the measurement apparatus, and a strength of an
electromagnetic wave in a third compartment corresponding to a cerebral
sulcus or a cerebral ventricle in the brain measured by the measurement
apparatus.

[0015] According to a fourth aspect of the invention, a program is
provided causing a computer to function as a compartmental analyzer that
performs compartmental analysis of dynamics of a tracer in a brain on the
basis of a strength of an electromagnetic wave from the tracer in the
brain measured by a measurement apparatus, and the program causes the
computer to function as a rate constant calculation unit that calculates
a rate constant when the tracer moves between the compartments on the
basis of a strength of an electromagnetic wave in a first compartment
corresponding to a cerebral blood vessel in the brain measured by the
measurement apparatus or an input function in the first compartment, a
strength of an electromagnetic wave in a second compartment corresponding
to brain tissue in the brain measured by the measurement apparatus, and a
strength of an electromagnetic wave in a third compartment corresponding
to a cerebral sulcus or a cerebral ventricle in the brain measured by the
measurement apparatus.

[0016] According to a fifth aspect of the invention, a recording medium
recording a program is provided causing a computer to function as a
compartmental analyzer that performs compartmental analysis of dynamics
of a tracer in a brain on the basis of a strength of an electromagnetic
wave from the tracer in the brain measured by a measurement apparatus,
and the recording medium recording a program causes the computer to
function as a rate constant calculation unit that calculates a rate
constant when the tracer moves between the compartments on the basis of a
strength of an electromagnetic wave in a first compartment corresponding
to a cerebral blood vessel in the brain measured by the measurement
apparatus or an input function in the first compartment, a strength of an
electromagnetic wave in a second compartment corresponding to brain
tissue in the brain measured by the measurement apparatus, and a strength
of an electromagnetic wave in a third compartment corresponding to a
cerebral sulcus or a cerebral ventricle in the brain measured by the
measurement apparatus.

[0017] In addition, the summary of the invention described above is not
intended to list all necessary features of the invention.

[0018] In addition, sub-combinations of these features may also be
regarded as the invention.

[0019] As is apparent from the above explanation, according to the
invention, parameters more useful than parameters that can be obtained by
the analysis using a two-compartment model can be calculated as
parameters for analyzing the dynamics of cerebral blood flow in the
brain.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a view showing an example of the environment of the use
of a compartmental analysis system 100 according to an embodiment.

[0021] FIG. 2 is a view showing an example of the block configuration of a
compartmental analyzer 110.

[0022] FIG. 3 is a view showing an example of the information, which is
stored in a region-of-interest information storage unit 119, in a table
form.

[0023] FIG. 4 is a view showing an example of the operation flow of the
compartmental analyzer 110.

[0024] FIG. 5 is a view showing an example of the hardware configuration
of a computer 800 that forms the compartmental analyzer 110 according to
the present embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, the invention will be described through embodiments of
the invention. However, the following embodiments do not limit the
invention defined in the appended claims, and all combinations of the
features described in the embodiments are not always necessary for the
solving means of the invention.

[0026] FIG. 1 shows an example of the environment of the use of a
compartmental analysis system 100 according to an embodiment. The
compartmental analysis system 100 is a system that performs compartmental
analysis of dynamics of H217O in the brain. Here,
H217O contains many water molecules with isotopes with large
mass numbers, and is water with a larger specific gravity than normal
water. In addition, H217O may be an example of "tracer" in this
invention.

[0027] The compartmental analysis system 100 includes a compartmental
analyzer 110, an MRI (Magnetic Resonance Imaging) apparatus 120, an input
device 130, and an output device 140. The compartmental analyzer 110 is
electrically connected to each of the MRI apparatus 120, the input device
130, and the output device 140. In addition, the MRI apparatus 120 may be
an example of a "measurement apparatus" in this invention.

[0028] The compartmental analyzer 110 is an apparatus that performs
compartmental analysis of the dynamics of H217O in the brain on
the basis of the strength of a nuclear magnetic resonance signal from
H217O in the brain measured by the MRI apparatus 120. In
addition, the nuclear magnetic resonance signal may be an example of an
"electromagnetic wave" in this invention.

[0029] The MRI apparatus 120 is an apparatus that recreates the
information inside the body as a three-dimensional image using a nuclear
magnetic resonance phenomenon. More specifically, the MRI apparatus 120
measures the strength of a nuclear magnetic resonance signal in the
brain.

[0030] The input device 130 is a device that inputs data, information,
instructions, and the like to the compartmental analyzer 110.

[0031] The output device 140 is a device that receives data or information
from the compartmental analyzer 110 and presents it in a form that can be
recognized by a human being.

[0035] The instruction-receiving unit 113 receives an instruction to
specify a region-of-interest of the brain, which is to be subjected to
compartmental analysis, through the input device 130.

[0036] The region division unit 114 divides the brain into a plurality of
voxels. More specifically, the region division unit 114 divides the
region-of-interest, which is specified by the instruction received by the
instruction-receiving unit 113, into a plurality of voxels. Here, the
voxel is a volume element, and indicates a value of a rectangular
parallelepiped unit in three-dimensional space. For example, when a cube
of 10 cm (vertical)×10 cm (horizontal)×5 cm (height) is a
region-of-interest, the "vertical×horizontal" plane can be divided
into a matrix. Here, each lattice plane obtained by division into a
matrix is called a pixel. In this case, a voxel is obtained by
multiplying a pixel by the height. In addition, the voxel may be an
example of a "divided region" in this invention.

[0037] The compartment-specifying unit 115 specifies to which one of a
first compartment corresponding to a cerebral blood vessel, a second
compartment corresponding to brain tissue, and a third compartment
corresponding to a cerebral sulcus or cerebral ventricle a part of the
brain in each of a plurality of voxels obtained by dividing the brain
corresponds. More specifically, the compartment-specifying unit 115
specifies to which one of the compartments a part of the brain in each of
a plurality of voxels divided by the region division unit 114
corresponds.

[0038] The strength data acquisition unit 116 acquires data, which
indicates the strength of the nuclear magnetic resonance signal for each
voxel in the brain, from the MRI apparatus 120.

[0039] The rate constant calculation unit 117 calculates the rate constant
when H217O moves between the compartments on the basis of the
strength of the nuclear magnetic resonance signal in the first
compartment in the brain measured by the MRI apparatus 120, the strength
of the nuclear magnetic resonance signal in the second compartment in the
brain measured by the MRI apparatus 120, and the strength of the nuclear
magnetic resonance signal in the third compartment in the brain measured
by the MRI apparatus 120. More specifically, the rate constant
calculation unit 117 calculates the rate constant when H217O
moves between the compartments on the basis of the strength of a nuclear
magnetic resonance signal in a voxel specified to correspond to the first
compartment by the compartment-specifying unit 115, the strength of a
nuclear magnetic resonance signal in a voxel specified to correspond to
the second compartment by the compartment-specifying unit 115, and the
strength of a nuclear magnetic resonance signal in a voxel specified to
correspond to the third compartment by the compartment-specifying unit
115.

[0040] FIG. 3 shows an example of information stored in the
region-of-interest information storage unit 119 in a table format. In the
region-of-interest information storage unit 119, information of voxel ID,
coordinates, compartments, and the strength are stored so as to match
with each other.

[0041] The voxel ID information is an identification code for uniquely
identifying each voxel in a plurality of voxels. The coordinate
information is information for specifying the position of the voxel
identified by the voxel ID. The compartment information is information
indicating a compartment to which a part of the brain in the voxel
identified by the voxel ID corresponds. The strength information is
information indicating the strength of the nuclear magnetic resonance
signal in the voxel identified by the voxel ID.

[0042] FIG. 4 shows an example of the operation flow of the compartmental
analyzer 110. FIGS. 1 to 3 will be referred to in explanation of this
operation flow.

[0043] A doctor photographs the inside of the brain of a patient using the
MRI apparatus 120 before injecting H217O into the patient. The
MRI apparatus 120 recreates the information in the brain as
three-dimensional image data using a nuclear magnetic resonance
phenomenon and outputs it to the compartmental analyzer 110.

[0044] When the three-dimensional image data obtained by photographing the
inside of the brain is acquired from the MRI apparatus 120 (S101), the
image data acquisition unit 111 of the compartmental analyzer 110
transmits the three-dimensional image data to the image data output unit
112 and also stores the three-dimensional image data in the image data
storage unit 118.

[0045] When the three-dimensional image data transmitted from the image
data acquisition unit 111 is received, the image data output unit 112 of
the compartmental analyzer 110 outputs the three-dimensional image data
to the output device 140 (S102). In this manner, the output device 140
outputs a three-dimensional image obtained by photographing the inside of
the brain.

[0046] A doctor determines a region-of-interest of the brain, which is to
be subjected to compartmental analysis, in the three-dimensional image of
the brain output from the output device 140. For example, when a patient
has an ischemic problem, a doctor determines the ischemic part as a
region-of-interest. Then, the doctor gives an instruction to specify the
determined region-of-interest using the input device 130.

[0047] When the instruction to specify a region-of-interest of the brain
to be subjected to compartmental analysis is received through the input
device 130 (S103), the instruction-receiving unit 113 of the
compartmental analyzer 110 transmits data indicating the specified
region-of-interest of the brain to the region division unit 114. For
example, the instruction-receiving unit 113 transmits data indicating a
plurality of coordinates in a three-dimensional image, which indicate the
outer edge of the specified region-of-interest of the brain, to the
region division unit 114 as data indicating the region-of-interest of the
brain.

[0048] When the data transmitted from the instruction-receiving unit 113
is received, the region division unit 114 of the compartmental analyzer
110 divides the region-of-interest, which is indicated by the data
received from the instruction-receiving unit 113, into a plurality of
voxels with reference to the three-dimensional image data stored in the
image data storage unit 118 (S104). For example, the region division unit
114 divides the region-of-interest into tens to hundreds of voxels or
more. In addition, the region division unit 114 stores the information of
the coordinates for specifying the position of each voxel in the
region-of-interest information storage unit 119 so as to match the
information of the voxel ID for identifying each voxel. Here, the
coordinate information may be coordinates of eight apices of a voxel, for
example.

[0049] When the voxel position information is stored in the
region-of-interest information storage unit 119, the
compartment-specifying unit 115 of the compartmental analyzer 110
specifies, with reference to the three-dimensional image data stored in
the image data storage unit 118, to which one of the first compartment
corresponding to the cerebral blood vessel, the second compartment
corresponding to brain tissue, and the third compartment corresponding to
the cerebral sulcus or cerebral ventricle a part of the brain in each of
the plurality of voxels obtained by dividing the brain corresponds
(S105). Here, the environment of water present in each part of the
cerebral blood vessel, brain tissue, cerebral sulcus, and cerebral
ventricle is different. The relaxation time of H is also different in
each of these parts. The MRI apparatus 120 generates a three-dimensional
image of the brain on the basis of such information. Accordingly, the
compartment-specifying unit 115 can specify to which part of the cerebral
blood vessel, brain tissue, cerebral sulcus, and cerebral ventricle the
part of the brain reflected in each voxel corresponds by performing image
analysis of the three-dimensional image data. Then, when a compartment
corresponding to the part of the brain in each voxel is specified, the
compartment-specifying unit 115 stores the information in the
region-of-interest information storage unit 119.

[0050] After the process of these steps S101 to S105 is completed, the
doctor injects H217O into the patient. Then, the doctor
measures the time-dependent strength of the nuclear magnetic resonance
signal for each voxel in the brain of the patient using the MRI apparatus
120. Here, 17O has an effect on H that is bonded thereto.

[0051] Accordingly, the strength of the nuclear magnetic resonance signal
due to H of H217O is different from that of the nuclear
magnetic resonance signal due to H of H216O present in the
brain. On the other hand, H217O injected into the patient is
diluted by H216O in the blood until H217O reaches the
brain. Therefore, in order to acquire a clear nuclear magnetic resonance
signal due to H of H217O in the MRI apparatus 120,
H217O needs to be concentrated to a higher concentration than
in natural water. Specifically, it is preferable to use H217O
concentrated to a concentration of 10% or more. In addition, a voxel as a
unit of a region where the MRI apparatus 120 measures the strength of a
nuclear magnetic resonance signal is the voxel divided in step S104. For
example, the MRI apparatus 120 measures the strength of the nuclear
magnetic resonance signal for each voxel in the brain while referring to
the voxel position information stored in the region-of-interest
information storage unit 119 of the compartmental analyzer 110. Then, the
MRI apparatus 120 outputs data, which indicates the strength of the
nuclear magnetic resonance signal for each voxel in the brain measured
over time, sequentially to the compartmental analyzer 110.

[0052] When the data indicating the strength of the nuclear magnetic
resonance signal for each voxel in the brain is sequentially acquired
from the MRI apparatus 120 (S106), the strength data acquisition unit 116
of the compartmental analyzer 110 stores the information of the strength
of the nuclear magnetic resonance signal for each voxel in the brain,
which is indicated by the data when H217O reaches the brain, in
the region-of-interest information storage unit 119. Here, "when
H217O reaches the brain" may be "when a predetermined time
elapses after injecting H217O" or may be "when the strength of
a nuclear magnetic resonance signal in a predetermined part in the brain
exceeds a predetermined threshold", for example.

[0053] When the information of the strength of the nuclear magnetic
resonance signal for each voxel is stored in the region-of-interest
information storage unit 119, the rate constant calculation unit 117 of
the compartmental analyzer 110 calculates a rate constant when
H217O moves between compartments on the basis of the strength
of the nuclear magnetic resonance signal in the first compartment, the
strength of the nuclear magnetic resonance signal in the second
compartment, and the strength of the nuclear magnetic resonance signal in
the third compartment (S107). Here, the strength of the nuclear magnetic
resonance signal may be regarded as the concentration of H217O
in the part. That is, when H217O is present in a certain part,
the strength of the nuclear magnetic resonance signal in the part may be
regarded as the concentration of H217O.

[0054] In the following explanation, the concentration of H217O
at a certain time t in the first compartment is set to Bl(t), the
concentration of H217O at the same time t in the second
compartment is set to Br(t), and the concentration of H217O at
the same time t in the third compartment is set to C(t). In addition, in
the following explanation, the rate constant when H217O moves
from the first compartment to the second compartment is set to K1, the
rate constant when H217O moves from the second compartment to
the first compartment is set to K2, the rate constant when
H217O moves from the first compartment to the third compartment
is set to K3, the rate constant when H217O moves from the third
compartment to the first compartment is set to K4, the rate constant when
H217O moves from the third compartment to the second
compartment is set to K5, and the rate constant when H217O
moves from the second compartment to the third compartment is set to K6.

[0055] In this case, time variation dBr(t)/dt of Br(t) can be expressed as
Expression (1), for example.

[Expression 1]

dBr(t)/dt=K1Bl(t)+K5C(t)-(K2+K6)Br(t) (1)

[0056] In addition, time variation dC(t)/dt of C(t) can be expressed as
Expression (2), for example.

[Expression 2]

dC(t)/dt=K3Bl(t)+K6Br(t)-(K5+K4)C(t) (2)

[0057] In addition, time variation dBl(t)/dt of Bl(t) can be expressed as
Expression (3), for example.

[Expression 3]

dBl(t)/dt=K2Br(t)+K4C(t)-(K1+K3)Bl(t) (3)

[0058] The rate constant calculation unit 117 applies the value of the
strength of the nuclear magnetic resonance signal for each voxel, which
is stored in the region-of-interest information storage unit 119, to
Bl(t), Br(t), and C(t) in Expressions (1) to (3) and also calculates the
rate constants K1 to K6 using normal mathematical techniques, such as the
Gauss-Newton method, the conjugate gradient method, the least squares
method, the modified Marquardt method, and the simplex method.

[0059] Thus, the rate constants K1 and K2 obtained by assuming the
relationship with the third compartment corresponding to the cerebral
sulcus or cerebral ventricle may be different values from K1 and K2
calculated by the analysis method using the two-compartment model in
which only the relationship between the cerebral blood vessel and the
brain tissue is assumed. In addition, the rate constants K3 to K6
obtained by assuming the relationship with the third compartment
corresponding to the cerebral sulcus or cerebral ventricle are rate
constants that could not be obtained by the analysis method using the
two-compartment model in which only the relationship between the cerebral
blood vessel and the brain tissue is assumed.

[0060] As described above, according to the compartmental analysis system
100, rate constants more useful than the rate constants obtained by the
analysis using the two-compartment models can be calculated as parameters
for analyzing the dynamics of cerebral blood flow in the brain. For
example, hemodynamics of blood flow or cerebrospinal fluid in each
specific location can be checked. In existing examinations, the spatial
resolution is poor (pixels (signal acquisition unit) of 10 (mm)×10
(mm) in the case of SPECT (Single Photon Emission Computed Tomography),
and pixels 1 (mm)×1 (mm) (may be smaller) in the case of MRI).
Accordingly, it is not possible to acquire a detailed local image of
cerebral blood flow. In addition, the flow of cerebrospinal fluid is not
taken into consideration at all. In contrast, according to the invention,
it is possible to check the detailed local cerebral blood flow and
cerebrospinal fluid dynamics more accurately. Accordingly, advanced
criteria for determining the treatment to be applied to the patient can
be obtained. For example, for a cerebral infarction patient, advanced
criteria of whether or not to perform thrombolytic therapy can be
obtained. That is, determination regarding whether or not a damaged
portion of the brain can be recovered by thrombolytic therapy can be made
more clearly than in the existing examination. In addition, since
functional information of cerebral blood vessels (cerebral blood flow and
cerebrospinal fluid circulation capability) is acquired, this may be used
to determine whether or not the cerebral blood vessels can withstand
thrombolytic therapy. Moreover, in recent years, it has also been
suggested that as a result of dementia, the amount of cerebrospinal fluid
circulation decreases. From this point of view, since cerebrospinal fluid
circulation can be accurately checked, the invention can contribute not
only to diagnosis but also to development of therapeutic agents for
increasing the amount of cerebrospinal fluid to the normal level.

[0061] In addition, although a radioactive chemical may be used as the
"tracer" in this invention instead of H217O, it is preferable
to use H217O due to the following reasons. Since existing
radiopharmaceuticals have short half-lives (for example, since the
half-life of 15O is extremely short (several minutes)), efficacy as
a diagnostic agent does not last long. For this reason, since existing
radiopharmaceuticals are not available, the existing radiopharmaceuticals
cannot be applied to emergency patients, such as cerebral infarction. In
the case of cerebral infarction, diagnosis and treatment within a few
hours from development of the symptoms are most effective. However,
existing radiopharmaceuticals have a fateful flaw in that diagnosis in
this acute phase cannot be performed. In addition, existing
radiopharmaceuticals are radioactive isotopes, and are not intrinsically
safe materials. The form of a diagnostic agent is also a disadvantage
because it is not a physiological substance but chemicals that the human
body does not usually take in, in SPECT agents and the like. In contrast,
since H217O is water, it is possible to acquire a result that
reflects the more precise physiological mechanism. In addition, although
the number of facilities where radioactive diagnostic agents can be used
is 1,000 or less in Japan, the agent for MRI proposed at this time may be
used in at least three times the number of facilities as the radioactive
diagnostic facilities. In addition, when a radiopharmaceutical is used as
a tracer, a PET (Positron Emission Tomography) apparatus or a SPECT
apparatus is used as the "measurement apparatus" in this invention
instead of the MRI apparatus 120.

[0062] In addition, the "rate constant calculation unit" in this invention
may be configured to use the signal strengths of a certain number of
voxels for each compartment when calculating the rate constant.

[0063] In addition, the "rate constant calculation unit" in this invention
may calculate a rate constant when a tracer moves between compartments
without using the strength of an electromagnetic wave in a first
compartment. In this case, instead of the strength of an electromagnetic
wave in the first compartment, the "rate constant calculation unit" in
this invention calculates the rate constant when a tracer moves between
compartments using a temporal measurement result of the amount of tracer
sampled from the patient's arterial blood after the tracer is
administered to the patient. Alternatively, the "rate constant
calculation unit" in this invention may calculate the rate constant when
a tracer moves between compartments using an input function to allow the
amount of tracer introduced into cerebral blood vessels to be assumed
instead of the strength of an electromagnetic wave in the first
compartment.

[0064] FIG. 5 shows an example of the hardware configuration of a computer
800 that forms the compartmental analyzer 110 according to the present
embodiment. The computer 800 according to the present embodiment
includes: a CPU periphery having a CPU (Central Processing Unit) 802, a
RAM (Random Access Memory) 803, a graphics controller 804, and a display
805 that are connected to each other through a host controller 801; an
input/output unit having a communication interface 807, a hard disk drive
808, and a CD-ROM (Compact Disk Read Only Memory) drive 809 that are
connected to each other through an input/output controller 806; and a
legacy input/output unit having a ROM (Read Only Memory) 810, a flexible
disk drive 811, and an input/output chip 812 that are connected to the
input/output controller 806.

[0065] The host controller 801 connects the RAM 803, the CPU 802, which
accesses the RAM 803 at a high transfer rate, and the graphics controller
804 to each other. The CPU 802 operates on the basis of programs stored
in the ROM 810 and the RAM 803, and controls each unit. The graphics
controller 804 acquires image data, which is generated on a frame buffer
provided in the RAM 803 by the CPU 802 or the like, and displays the
image data on the display 805. Instead of this, the graphics controller
804 may include a frame buffer that stores the image data generated by
the CPU 802 or the like.

[0066] The input/output controller 806 connects the host controller 801,
the communication interface 807, which is a relatively high-speed
input/output device, the hard disk drive 808, and the CD-ROM drive 809 to
each other. The hard disk drive 808 stores data and programs used by the
CPU 802 in the computer 800. The CD-ROM drive 809 reads a program or data
from a CD-ROM 892 and provides it to the hard disk drive 808 through the
RAM 803.

[0067] In addition, the ROM 810, the flexible disk drive 811, and a
relatively low-speed input/output device of the input/output chip 812 are
connected to the input/output controller 806. A boot program executed at
the start time of the computer 800 and/or a program depending on the
hardware of the computer 800 are stored in the ROM 810. The flexible disk
drive 811 reads a program or data from a flexible disk 893 and provides
it to the hard disk drive 808 through the RAM 803. The input/output chip
812 connects the flexible disk drive 811 to the input/output controller
806 and also connects various kinds of input/output devices to the
input/output controller 806 through a parallel port, a serial port, a
keyboard port, or a mouse port, for example.

[0068] A program provided to the hard disk drive 808 through the RAM 803
is stored on a recording medium, such as the flexible disk 893, the
CD-ROM 892, or an IC (Integrated Circuit) card, and is provided by the
user. The program is read from the recording medium, is installed in the
hard disk drive 808 in the computer 800 through the RAM 803, and is
executed in the CPU 802.

[0069] The program, which is installed in the computer 800 and causes the
computer 800 to function as the compartmental analyzer 110, causes the
computer 800 to function as the rate constant calculation unit 117 that
calculates a rate constant when H217O moves between the
compartments on the basis of the strength of the nuclear magnetic
resonance signal in the first compartment in the brain measured by the
MRI apparatus 120, the strength of the nuclear magnetic resonance signal
in the second compartment in the brain measured by the MRI apparatus 120,
and the strength of the nuclear magnetic resonance signal in the third
compartment in the brain measured by the MRI apparatus 120 in step S107.

[0070] In addition, the program may cause the computer 800 to function as
the compartment-specifying unit 115 that specifies to which one of the
first compartment corresponding to the cerebral blood vessel, the second
compartment corresponding to brain tissue, and the third compartment
corresponding to the cerebral sulcus or cerebral ventricle a part of the
brain in each of the plurality of voxels obtained by dividing the brain
corresponds in step 5105 and the rate constant calculation unit 117 that
calculates a rate constant when H217O moves between the
compartments on the basis of the strength of the nuclear magnetic
resonance signal in a voxel specified to correspond to the first
compartment by the compartment-specifying unit 115, the strength of the
nuclear magnetic resonance signal in a voxel specified to correspond to
the second compartment by the compartment-specifying unit 115, and the
strength of the nuclear magnetic resonance signal in a voxel specified to
correspond to the third compartment by the compartment-specifying unit
115 in step S107.

[0071] In addition, the program may cause the computer 800 to function as
the region division unit 114 that divides a brain into a plurality of
voxels in step S104 and the compartment-specifying unit 115 that
specifies to which one of the compartments a part of the brain in each of
the plurality of voxels divided by the region division unit 114
corresponds in step S105.

[0072] In addition, the program may cause the computer 800 to function as
the instruction-receiving unit 113 that receives an instruction to
specify a region-of-interest of the brain, which is to be subjected to
compartmental analysis, through the input device 130 in step S103 and the
region division unit 114 that divides the region-of-interest, which is
specified by the instruction received by the instruction-receiving unit
113, into a plurality of voxels in step S104.

[0073] In addition, the program may cause the computer 800 to function as
the image data acquisition unit 111 that acquires three-dimensional image
data of the photographed brain from the MRI apparatus 120 in step S101.

[0074] In addition, the program may cause the computer 800 to function as
the image data output unit 112 that outputs the three-dimensional image
data of the photographed brain to the output device 140 in step S102.

[0075] In addition, the program may cause the computer 800 to function as
the strength data acquisition unit 116 that acquires data, which
indicates the strength of a nuclear magnetic resonance signal for each
voxel in the brain, from the MRI apparatus 120 in step S106.

[0076] The information processing described in these programs is loaded
into the computer 800 to function as the image data acquisition unit 111,
the image data output unit 112, the instruction-receiving unit 113, the
region division unit 114, the compartment-specifying unit 115, the
strength data acquisition unit 116, the rate constant calculation unit
117, the image data storage unit 118, and the region-of-interest
information storage unit 119 which are specific means of software and
various kinds of hardware resources described above that cooperate with
each other. In addition, by realizing an operation or processing of the
information according to the purpose of use of the computer 800 in the
present embodiment using the specific means, the compartmental analyzer
110 specific to the purpose of use is constructed.

[0077] As an example, when performing communication between the computer
800 and an external apparatus or the like, the CPU 802 executes a
communication program loaded on the RAM 803 and instructs the
communication interface 807 to perform communication processing on the
basis of the content of processing described in the communication
program. By control of the CPU 802, the communication interface 807 reads
the transmission data, which is stored in a transmission buffer region or
the like set on a storage device such as the RAM 803, the hard disk drive
808, the flexible disk 893, or the CD-ROM 892 and transmits it through
the network or writes the received data, which is received through the
network, into a receiving buffer region set on a storage device. Thus,
data may be transmitted or received to or from the storage device through
the communication interface 807 using the direct memory access method.
Instead, data may also be transmitted or received by allowing the CPU 802
to read the data from a storage device at the source or through the
communication interface 807 and write the data into a storage device at
the destination or through the communication interface 807 at the
destination.

[0078] In addition, the CPU 802 loads all or some necessary files or a
database stored on an external storage device, such as the hard disk
drive 808, the CD-ROM 892, or the flexible disk 893, into the RAM 803 by
direct memory access transfer or the like and performs various kinds of
processing on the data in the RAM 803. Then, the CPU 802 writes the data
after the processing into the external storage by direct memory access
transfer or the like.

[0079] In such processing, it can be regarded that the RAM 803 holds the
content of an external storage device temporarily. In the present
embodiment, therefore, the RAM 803, the external storage device, and the
like are collectively called a memory, a storage unit, a storage device,
or the like. In the present embodiment, various kinds of information,
such as various programs, data, tables, and a database, are stored on
such a storage device to become objects of information processing. In
addition, the CPU 802 can hold a part of the RAM 803 in a cache memory
and perform reading and writing on the cache memory. Also in such a form,
the cache memory has a part of the function of the RAM 803. In the
present embodiment, therefore, the cache memory shall also be included in
the RAM 803, a memory, and/or a storage device except for the case where
the cache memory is distinctively described.

[0080] In addition, the CPU 802 performs various kinds of processing,
which have been specified by the instruction sequence of the program and
which include various kinds of operations, processing of information,
determination of conditions, information retrieval, and replacement, on
the data read from the RAM 803 and writes the result into the RAM 803.
For example, in the case of determination of conditions, the CPU 802
determines whether or not various variables shown in the present
embodiment satisfy predetermined conditions are greater than other
variables or constants, whether or not various variables are smaller than
other variables or constants, whether or not various variables are equal
to or greater than other variables or constants, whether or not various
variables are equal to or less than other variables or constants, or
whether or not various variables are equal to other variables or
constants. When the conditions are satisfied or not satisfied, the CPU
802 branches to different instruction sequences or calls a subroutine.

[0081] In addition, the CPU 802 can retrieve the information stored in
files, a database, and the like on the storage device. For example, when
a plurality of entries in which the attribute value of a second attribute
is matched with the attribute value of a first attribute are stored on
the storage device, the CPU 802 can obtain the attribute value of the
second attribute matched with the first attribute, which satisfies
predetermined conditions, by retrieving an entry matching the conditions,
in which the attribute value of the first attribute is specified, from
the plurality of entries stored on the storage device and reading the
attribute value of the second attribute stored in the entry.

[0082] The above-described programs or modules may be stored on the
external storage medium. Not only the flexible disk 893 and the CD-ROM
892 but also optical recording media such as a DVD (Digital Versatile
Disc) or a CD (Compact Disc), magneto-optical recording media such as an
MO (Magneto-Optical disc), tape media, a semiconductor memory such as an
IC card, and the like may be used as storage media. In addition, storage
media, such as a hard disk, a RAM, and the like, provided in a server
system connected to a private communication network or the Internet may
be used as recording media, and a program may be provided to the computer
800 through the network.

[0083] While the invention has been described using the embodiment, the
technical scope of the invention is not limited to the scope described in
the embodiment described above. It is apparent to those skilled in the
art that various modifications or improvements may be made to the
embodiment described above. It is apparent from the appended claims that
such modifications or improvements may also be included in the technical
scope of the invention.

[0084] It should be noted that the order of execution of each process of
the operations, procedures, steps, and the like in the system, the
method, the apparatus, the program, and the recording medium described in
the appended claims, specification, and drawings may be implemented in
any order unless "before", "in advance", and the like are particularly
expressed and the output of a previous process is used in the next
process. For the operation flows in the appended claims, specification,
and drawings, even if the operation flows are described using "first",
"next", and the like for convenience, it does not mean that the operation
flows should be executed in this order.

[0085] While preferred embodiments of the invention have been described
and illustrated above, it should be understood that these are exemplary
of the invention and are not to be considered as limiting. Additions,
omissions, substitutions, and other modifications can be made without
departing from the spirit or scope of the present invention. Accordingly,
the invention is not to be considered as being limited by the foregoing
description, and is only limited by the scope of the appended claims.

Patent applications by Takashi Kambe, Tsuchiura-Shi JP

Patent applications by TAIYO NIPPON SANSO CORPORATION

Patent applications in class Using detectable material placed in body

Patent applications in all subclasses Using detectable material placed in body